The present invention relates to a magnetic alloy and more particularly to a magnetic alloy of the Fe-Cr-Co type such as is known in the art as a spinodal decomposition type magnetic alloy.
The Fe-Cr-Co type magnetic alloy has been known as having a quite superior quality in machinability compared to conventional magnetic alloys, and its fundamental constitution is described in U.S. Pat. No. 3,806,336. In the Fe-Cr-Co magnetic alloy it has been known also that at the time of spinodal decomposition of the ferromagnetic .alpha.-phase into two phases, i.e. .alpha..sub.1 -phase (ferromagnetic phase) and .alpha..sub.2 -phase (nonmagnetic phase), it is desirable that the decomposition temperature Tsp and the Curie point Tc of the .alpha.-phase coincide from the point of view of magnetic properties. Further it has been also known that the .alpha..sub.1 -phase, i.e. ferromagnetic phase, produced by the spinodal decomposition is possible to be controlled in its growth direction by a magnetic field applied externally. On the other hand it has been also known that there exist .gamma.- and .sigma.-phases, which are nonmagnetic as well as stable, intermediate the .alpha.-phase which is stable at a higher temperature and the lower temperature range at which the spinodal decomposition begins to occur.
As a result, in order to use a Fe-Cr-Co type magnetic alloy as excellent material for a permanent magnet, it is understandable that it should be constituted so as not to contain a .gamma.- and/or .sigma.-phase as abovesaid and at the same time it should have a Tsp equal or nearly equal to Tc. Hitherto many studies have already been done for the purpose of realizing the above principle and also many publications dealing with the realization have been issued.